How does an adult hydra produce a new hydra?
a. by developing a seed
b. by making a spore
c. by growing a bud
d. by splitting itself into two equal parts

Gases enter the atmosphere and trap the sun's heat warning the earth.

Mars and earth have quite a few things in common. both are  terrestrial planets, both are located within the sun’s  habitable zone, both have  polar ice caps, similarly  tilted axes, and similar  variations in temperature. and according to some of the latest scientific data obtained by rovers and atmospheric probes, it is now known that mars once had a  dense atmosphere  and was covered with  warm, flowing water.